The present invention relates to a drill chuck. More particularly this invention concerns such a chuck which can be easily removed from its drive spindle.
In order to switch between different tools it is known to make a drill chuck so that it can be quickly loosened and tightened, or to make the chuck and tool such that they can be snapped together and apart readily. Thus the user can, for instance, switch between a drill bit for making a screw hole and a driver bit for setting a screw in the hole.
Another solution proposed in German utility model 200 16 090 published Nov. 16, 2000 is to provide a standard three-jaw chuck with mechanism that allows the entire chuck to be taken off its drive spindle and swapped with another such chuck, presumably holding a different tool. This system is particularly handy when round-shank tools are being employed that have to be clamped solidly so that simply dechucking and rechucking them is not quickly done and where a tool, e.g. a chuck key, is often needed.
To achieve this object the chuck body has a rearwardly open bore shaped to fit complementarily with a nonround drive spindle. A radially displaceable latch element in the chuck body can be moved from a holding position engaged radially inward into a radially outwardly open seat in the drive spindle to an unlatched position clear of this seat. When the latch element is engaged in the seat the spindle is locked axially to the chuck body and when in the freeing position the chuck can be taken off the spindle.
The main disadvantage of this type of quick-release mechanism is that it adds considerably to the overall length of the drill chuck. A chuck""s length is at a minimum equal to the distance between the front end of the chuck body and the rear ends of the jaws in the rear end, maximum-spread position of the jaws. The quick-release mechanism must be at the rear end of the chuck and invariably takes up some extra space here. This makes the drill using the chuck overlong and front-end heavy.
It is therefore an object of the present invention to provide an improved quick-release drill chuck.
Another object is the provision of such an improved quick-release drill chuck which overcomes the above-given disadvantages, that is which can easily be taken off and locked on a drive spindle, but that has an axial dimension that is no greater than a standard permanent-mount chuck.
A chuck releasably securable to a drive spindle has according to the invention a chuck body centered on an axis and formed with a rearwardly open bore adapted to fit with the drive spindle and a plurality of forwardly open, angularly spaced, and inwardly angled guides. Respective jaws are displaceable in the guides between relatively widely spaced rear end positions and relatively closely spaced front end positions. A ring rotatable on the body has an internal screwthread meshing with the jaws for displacement of the jaws between their positions on rotation of the ring. A latch element is radially displaceable on the body between a holding position projecting radially into the bore and locking the spindle therein and a freeing position clear of the bore and permitting the spindle to withdraw from the bore. A latch sleeve engageable with the latch element is displaceable on the body between a latched position forcing the element into the holding position and an unlatched position allowing the element to move into the freeing position. A spring braced between the latch sleeve and the body urges the latch sleeve into the latched position. The spring is mostly forward of rear ends of the jaws in the rear-end positions thereof.
Thus the biasing spring according to the invention does not take up any significant room and the chuck according to the invention can be of a length comparable to a standard permanently mounted chuck. The biasing spring is located generally level with the jaws so that the sleeve can replace the standard rear-end cap and does not add anything significant to the chuck""s length.
According to the invention the spring lies wholly forward of rear ends of the jaws in the rear-end positions thereof. In this embodiment the chuck is the same length as a standard permanently mounted chuck.
The sleeve in accordance with the invention is axially displaceable between its positions and the spring is an axially extending coil spring centered on the axis and having a rear end braced axially against the latch sleeve and front end braced axially against the chuck body. In this case the sleeve has a shoulder bearing on the rear end of the spring and the chuck body is provided with a snap ring against which the front end of the spring bears. The spring is of frustoconical shape with a taper corresponding to an angle the guides form with the axis.
In another system according to the invention the sleeve is angularly displaceable between its positions and the spring has one end braced angularly against the latch sleeve and an opposite end braced angularly against the chuck body so that the spring itself extends angularly. Normally there are a plurality of the springs and the sleeve and chuck body form respective angularly extending pockets receiving the springs. The jaws can dip back into these pockets when fully retracted, making the structure very compact.
The sleeve can have a plastic outer part and a metallic inner part engageable with the element. This construction reduces mass of the sleeve and keeps the chuck as light as possible. Normally the element is a plurality of balls radially displaceable in respective angularly equispaced passages in the chuck body. These balls themselves are axially forward of the rear ends of the jaws in their rear-end positions so that they also do not add any length to the chuck.